Puerto Rico declared Monday that its 2016 Zika outbreak had ended, citing falling virus transmissions. Since April, 10 Zika cases have been reported in a four-week period, compared with 8,000 cases in a four-week period during the epidemic’s peak in August 2016.
But health experts caution that reduced transmissions don’t necessarily indicate the virus is no longer a threat. They point out that it’s not yet peak mosquito season and a more apt comparison can be made in August.
There’s also concern about the accuracy of Puerto Rico’s surveillance system, which led the U.S. to stop reporting Puerto Rico’s Zika numbers last fall.
“It is important that we remain vigilant in preventing, detecting, and responding to new cases and in supporting families already affected by Zika,” a spokesperson for the U.S. Centers for Disease Control and Prevention said in a statement.
The CDC travel notice for Puerto Rico remains in effect, and the agency recommends that women who are pregnant or trying to conceive avoid traveling to Puerto Rico, and that men who have traveled to Puerto Rico use condoms afterward.
“You don’t want people to become complacent,” Dr. Anna Durbin, a professor at Johns Hopkins Bloomberg School of Public Health, told HuffPost.
“There are not as many cases, but Zika is still an important problem, because we’re still seeing transmission.”
Zika is a critical concern for pregnant women, because it’s linked to the severe birth defect microcephaly, which can cause developmental disabilities and babies being born with smaller-than-average heads.
“We expect to see babies born in 2017 with Zika virus-related congenital birth defects, and we must ensure they receive the best care possible,” the CDC statement read.
According to the Puerto Rican Health Department, the territory has had 3,678 pregnant women infected with Zika virus and 35 reported cases of Zika-related birth defects. In comparison, the United States reported 1,883 Zika-affected pregnancies and 72 babies born with Zika-related birth defects.
There’s been some controversy about whether Puerto Rico has been underreporting Zika-related birth defects, which fall far short of predictions. A 2016 JAMA Pediatrics study estimated that Puerto Rico would see between 110 and 290 Zika-related microcephaly cases by mid-2017.
The CDC is working with Puerto Rico to standardize its reporting.
Then there’s the question of whether the Puerto Rican Health Department’s announcement helps or hurts citizens. Officials may want to reassure the population and jump-start tourism, but they also need to address the ongoing risk to citizens and travelers.
“The message should be, yes, it looks as though the epidemic is waning, but you still need to protect yourself,” Durbin said. “Even if the risk could be much smaller, the consequences could be devastating.”
Durbin also noted that Puerto Rico is moving into its summer season, when mosquitos are most active. “I think they are also expecting it to pick up again,” she said.